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Microbial Degradation of Biodegradable Polymers

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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Macromolecules".

Deadline for manuscript submissions: closed (15 October 2022) | Viewed by 12372

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Special Issue Editors

Prof. Dr. Terence L. Marsh

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Guest Editor

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
Interests: microbial communities; gut microbiota; microbiomes; aquatic vertebrates
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Rafael Auras

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Guest Editor

Department of Microbiology and Molecular Genetics, Biomedical & Physical Sciences, Michigan State University, East Lansing, MI 48824-1223, USA
Interests: polymers; poly(lactic acid); packaging; biodegradation; life cycle assessment

Special Issue Information

Dear Colleagues,

Sustainable ecosystems are an increasingly critical global goal as the human population’s demands increase, and climate change impacts global processes. Human-made polymers have become ubiquitous and quite problematic due to their slow recycling rates and impact when leaching to the environment. To alleviate this, considerable focus has been placed on green chemistry and easily recyclable biodegradable polymers that can replace, if not improve, the functionality of longer-lived polymers. The “new biodegradable plastics” include poly(lactic acid), starch blends, poly(butylene succinate), poly(butylene-co-adipate terephthalate), and polyhydroxyalkonates. All of these “new” plastics are biodegradable by microorganisms at a measurable human scale living rate. This Special Issue focuses on the degradation strategies of microorganisms, including the biochemistry of attachment to the polymer, depolymerization, bio-assimilation, degradation rates, and methods to enhance these rates. We encourage original research submissions, critical and systematic reviews, and interdisciplinary work spanning chemistry, microbiology, and ecology, focused on deep molecular research.

Prof. Dr. Terence Marsh
Prof. Dr. Rafael Auras
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

biodegradable polymers
degradation strategies of microorganisms
depolymerization

Published Papers (3 papers)

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Research

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21 pages, 4741 KiB

Open AccessArticle

Effect of Chain Extending Cross-Linkers on the Disintegration Behavior of Composted PBAT/PLA Blown Films

by Juliana V. C. Azevedo, Berenika Hausnerova, Bernhard Möginger and Tomas Sopik

Int. J. Mol. Sci. 2023, 24(5), 4525; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24054525 - 24 Feb 2023

Cited by 1 | Viewed by 1566

Abstract

A biodegradable blend of PBAT—poly(butylene adipate-co-terephthalate)—and PLA—poly(lactic acid)—for blown film extrusion was modified with four multi-functional chain extending cross-linkers (CECL). The anisotropic morphology introduced during film blowing affects the degradation processes. Given that two CECL increased the melt flow rate (MFR) of tris(2,4-di-tert-butylphenyl)phosphite (V1) and 1,3-phenylenebisoxazoline (V2) and the other two reduced it (aromatic polycarbodiimide (V3) and poly(4,4-dicyclohexylmethanecarbodiimide) (V4)), their compost (bio-)disintegration behavior was investigated. It was significantly altered with respect to the unmodified reference blend (REF). The disintegration behavior at 30 and 60 °C was investigated by determining changes in mass, Young’s moduli, tensile strengths, elongations at break and thermal properties. In order to quantify the disintegration behavior, the hole areas of blown films were evaluated after compost storage at 60 °C to calculate the kinetics of the time dependent degrees of disintegration. The kinetic model of disintegration provides two parameters: initiation time and disintegration time. They quantify the effects of the CECL on the disintegration behavior of the PBAT/PLA compound. Differential scanning calorimetry (DSC) revealed a pronounced annealing effect during storage in compost at 30 °C, as well as the occurrence of an additional step-like increase in the heat flow at 75 °C after storage at 60 °C. The disintegration consists of processes which affect amorphous and crystalline phase of PBAT in different manner that cannot be understood by a hydrolytic chain degradation only. Furthermore, gel permeation chromatography (GPC) revealed molecular degradation only at 60 °C for the REF and V1 after 7 days of compost storage. The observed losses of mass and cross-sectional area seem to be attributed more to mechanical decay than to molecular degradation for the given compost storage times. Full article

(This article belongs to the Special Issue Microbial Degradation of Biodegradable Polymers)

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20 pages, 1765 KiB

Open AccessArticle

Genome Annotation of Poly(lactic acid) Degrading Pseudomonas aeruginosa, Sphingobacterium sp. and Geobacillus sp.

by Sadia Mehmood Satti, Edgar Castro-Aguirre, Aamer Ali Shah, Terence L. Marsh and Rafael Auras

Int. J. Mol. Sci. 2021, 22(14), 7385; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22147385 - 10 Jul 2021

Cited by 6 | Viewed by 2727

Abstract

Pseudomonas aeruginosa and Sphingobacterium sp. are well known for their ability to decontaminate many environmental pollutants while Geobacillus sp. have been exploited for their thermostable enzymes. This study reports the annotation of genomes of P. aeruginosa S3, Sphingobacterium S2 and Geobacillus EC-3 that were isolated from compost, based on their ability to degrade poly(lactic acid), PLA. Draft genomes of the strains were assembled from Illumina reads, annotated and viewed with the aim of gaining insight into the genetic elements involved in degradation of PLA. The draft genome of Sphinogobacterium strain S2 (435 contigs) was estimated at 5,604,691 bp and the draft genome of P. aeruginosa strain S3 (303 contigs) was estimated at 6,631,638 bp. The draft genome of the thermophile Geobacillus strain EC-3 (111 contigs) was estimated at 3,397,712 bp. A total of 5385 (60% with annotation), 6437 (80% with annotation) and 3790 (74% with annotation) protein-coding genes were predicted for strains S2, S3 and EC-3, respectively. Catabolic genes for the biodegradation of xenobiotics, aromatic compounds and lactic acid as well as the genes attributable to the establishment and regulation of biofilm were identified in all three draft genomes. Our results reveal essential genetic elements that facilitate PLA metabolism at mesophilic and thermophilic temperatures in these three isolates. Full article

(This article belongs to the Special Issue Microbial Degradation of Biodegradable Polymers)

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Review

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106 pages, 19527 KiB

Open AccessReview

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

by Anibal Bher, Pooja C. Mayekar, Rafael A. Auras and Carlos E. Schvezov

Int. J. Mol. Sci. 2022, 23(20), 12165; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232012165 - 12 Oct 2022

Cited by 39 | Viewed by 6806

Abstract

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment’s factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO₂ evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed. Full article

(This article belongs to the Special Issue Microbial Degradation of Biodegradable Polymers)

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